function increaseInterval(event) { upDateInterval(15);	}
function decreaseInterval(event) { upDateInterval(-15);	}

function upDateInterval(intervalChange) {			
	currentInterval = currentInterval + intervalChange;
	if (currentInterval >= 120) {
		currentInterval = 120;
	}
	var intervalString = "within " + currentInterval + " minutes"		
	if (currentInterval <= 0) {
		currentInterval = 0;
		intervalString = "NOW";
	}
	document.getElementById("currentInterval").innerHTML = intervalString;
}